Question

Why moon only attract water why not other objects like tree?

Answer 1

it does, but the force is immeasurably small on something tiny like a balloon or a human, it's all a matter of scale, the oceans consist of many billions of tons of water, spread over thousands of square miles but the tide is only a few metres high out in the open ocean ( those few metres can be magnified by the topology of the coasts and ocean floor)
http://en.m.wikipedia.org/wiki/Tide

Tides in the smaller oceans  like the Mediterranean sea are very small
Less than a metre. Even very large lakes have microscopic tides, no tides at all on the smaller lakes.